Tuesday, August 6, 2013

New paper finds another 2 non-hockey-sticks in the Arctic Nordic Seas

A new paper published in Climate of the Past reconstructs sea surface temperatures in the Eastern & Western Nordic Seas of the Arctic over the past 9,000 years, and each of the proxies show a long-term cooling trend over the past 8,000 years since the Holocene Climate Optimum.

Orange dots in bottom graph show reconstructed Sea Surface Temperatures [SSTs] in the eastern Nordic seas [Anderson et al, 2004] and purple dots show SSTs in the Western Nordic Seas [Calvo et al, 2002]. Top two graphs a & b show 8 modeled Sea Surface Temperatures [SSTs] in the Eastern & Western Nordic Seas, cooling over the past 7,000 years. Horizontal axis is thousands of years before the present.

M. Blaschek and H. RenssenCluster Earth & Climate, Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, The NetherlandsAbstract. The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene thermal maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveals a complex interaction of mechanisms active in the HTM. Previous studies have investigated the impact of the Laurentide Ice Sheet (LIS), as a remnant from the previous glacial period, altering climate conditions with a continuous supply of melt water to the Labrador Sea and adjacent seas and with a downwind cooling effect from the remnant LIS. In our present work we extend this approach by investigating the impact of the Greenland Ice Sheet (GIS) on the early Holocene climate and the HTM. Reconstructions suggest melt rates of 13 mSv for 9 ka BP, which result in our model in an ocean surface cooling of up to 2 K near Greenland. Reconstructed summer SST gradients agree best with our simulation including GIS melt, confirming that the impact of the early Holocene GIS is crucial for understanding the HTM characteristics in the Nordic Seas area. This implies that modern and near-future GIS melt can be expected to play an active role in the climate system in the centuries to come.